Design Guide 123
I/O Controller Hub
9.2 SPKR Pin Consideration
SPKR is used as both the output signal to the system speaker and as a functional strap. The strap
function enables or disables the “TCO Timer Reboot function” based on the state of the SPKR pin
on the rising edge of PWROK. When enabled, the ICH3-S sends an SMI# to the processor upon a
TCO timer timeout. The status of this strap is readable via the NO_REBOOT bit (bit 1, D31: F0,
Offset D4h). The SPKR signal has a weak integrated pull-down resistor (the resistor is only
enabled during boot/reset). Therefore, its default state is a logical zero or set to reboot. To disable
TCO timer reboot, a jumper can be populated to pull the signal line high (see Figure 9-4). The
value of the pull-up must be such that the voltage divider output caused by the pull-up, the effective
pull-down (REFF), and the ICH3-S’s integrated pull-down resistor will be read as logic high
(0.5 VCC_3.3 to VCC_3.3 + 0.5 V).
9.3 PCI
The ICH3-S provides a PCI Bus interface that is compliant with the PCI Local Bus Specification,
Revision 2.2. The implementation is optimized for high-performance data streaming when the
ICH3-S is acting as either the target or the initiator on the PCI bus. For more information on the
PCI Bus interface, refer to the PCI Local Bus Specification, Revision 2.2.
The ICH3-S supports six PCI Bus masters (excluding the ICH3-S), by providing six REQ# / GNT#
pairs. In addition, the ICH3-S supports two PC/PCI REQ# / GNT# pairs, one of which is
multiplexed with a PCI REQ# / GNT# pair.
Figure 9-4. Example Speaker Circuit
SPKR
Intel
®
ICH3-S
Effective impedance
due to speaker.
R
eff
Integrated
Pulldown
13 kΩ - 38 kΩ
VCC3_3
R value is
implementation
specific.
Stuff jumper to disable
timeout feature (no reboot).
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